Ultrasonic Flowmeters:

Already we have seen some of the ultrasonic devices before like Ultrasonic Level Sensor and Ultrasonic Distance Sensing. Now, I am going to explain one more ultrasonic device here. Ultrasonic Flow-meters are used to detect the speed of flow or subsequently quantity passed through the flow in given time.

Types of Ultrasonic Flowmeter:

1. Transit Time Type.
2. Doppler Frequency Shift Type.

1. Transit Time Type Ultrasonic Flowmeters:

In this type, two sensors are mounted on the pipe or channel. They send and receive the ultrasonic pulses simultaneously. When the speed of flow is zero or flow is steady, both the sensors receive the reflected pulses at the same time. Vice versa, when the fluid is in motion, sensors receive the pulse with delay between them. This delay is called as transit time difference. This transit time difference is directly proportional to velocity of flow and hence the volume of flow per unit time.

2. Doppler Frequency Shift Method:

Doppler effect could be explained as the frequencies of received sound waves depends on the motion of the source or observer relative to the propagating medium. The transmitter transmits ultrasonic waves. These are reflected from particles and bubbles. Frequency shifting takes place in reflected wave which is linearly proportional to the rate of flow of materials.

Advantages:

1. The flow of pure water, wash water, sewage, process liquids, oils, and other light homogeneous liquids can be measured.
2. It have no moving parts and hence have very less or no maintenance.
3. Can be used for variety of pipes.
4. It have flexibility to be used on existing pipelines.
5. It can be used as a portable device.
6. It does not have any contact with liquid and hence no danger from corrosive liquids.

Seminar on Ultrasonic Flow meter:

Above is given the information about ultrasonic flow meters. Here are short framework for seminar on ultrasonic flowmeter.

1. Introduction to Ultrasonics.
2. Ultrasonics Properties.
3. Ultrasonic Flowmeter.
4. Construction and working.
5. Types.
6. Transit time type.
7. Doppler Frequency Shift Method.
8. Advantages.
9. Limitations.
10. Applications.

Related Topics and Articles:

1. Ultrasonic Devices
2. Ultrasonic Distance Sensing
3. Ultrasonic Level Sensor

Introduction:

In previous article, we studied the Ultrasonic Level Sensors and its details. Now, I am going to explain the another ultrasonic device which works almost similar way to before. Ultrasonic Distance Sensor.

Ultrasonic Distance Sensing:

Ultrasonic Sensors are devices used to take measurements of Remote Distances or we call it as remote distance sensing. Ultrasonic sensing is based on time of flight principle. The transmitter produces the ultrasonic sound or burst or noise, which travels away from source and it enconters the barriers it gets reflected back. Then it is received by receiver.

Whole important topic here is Time Between Wave Produced and Wave Received. This time is used to calculate the distance between the ultrasonic device and obstruction. Other some constants like speed of ultrasonic sound in the air, humidity etc. are major factors in this calculation. If there is a relative movement between the source and the reflector, Doppler Effect can be employed to measure the distance.

Principle of Working of Ultrasonic Distance Sensor:

Ultrasonic sensors work on a principle similar to radar or SONAR which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object.

Formula For Ultrasonic Device Measurement:

d=(vt cos θ)/2

where;

d = Final distance,

t= time,

θ = angle of incidence,

Advantages:

1. Ultrasonic Distance measurement devices are more efficient.
2. Ultrasonic Distance measurement devices produce reliable accuracy.
3. Ultrasonic Distance measurement devices have robust construction and have long life of operation.
4. Ultrasonic Distance measurement devices have better accuracy than the other remote distance measuring devices.
5. Ultrasonic Distance measurement devices produce results faster than other devices.
6. Most important thing about Ultrasonic Distance measurement devices is that, they can produce result without interfering the object.

Disadvantages:

1. Ultrasonic Distance measurement devices have limitations when there is density of matter or medium is not consistant.
2. Also the reading may get distorted due to shapes of solids to be measured as reflection of ultrasonic wave is mostly dependent on shape of solid object which is treated as obstruction.

Applications:

Ultrasonic Distance measurement devices have many applications of which most popular are SONAR, Submarine Signaling, robotics etc.

Ultrasonic Distance measurement devices as Electronics Seminar Topics:

Ultrasonic Distance measurement seminar must contain following things.

1. Ultrasonic Sound Introduction.
2. Ultrasonic Devices.
3. Construction and working of Ultrasonic Device.
4. Principle of working.
5. Advantages.
6. Limitations.
7. Applications.

Related Topics and Articles:

1. Ultrasonic Devices
2. Ultrasonic Flowmeters
3. Ultrasonic Level Sensor

Seminar on Ultrasonic Level Sensor:

Ultrasonic Level Sensor is good seminar topic for Electronics Engineering:

1. What is Sensor?
2. Ultrasonic Level Sensor
3. Construction.
4. Working.
5. Advantages.
6. Limitations.
7. Applications.

What is Sensor or Transducer:

Transducer is device which converts the mechanical signal to the electrical signal. Transducer includes various devices like LVDT, tachogenerator, RVDT etc.

Ultrasonic Level Sensor:

Ultrasonic Level Sensor is the device which is used to measure the level of matter in tank or similar. As name suggest, it uses the ultrasonic waves for this measurement.

Construction and Working of Ultrasonic Level Sensor :

Ultrasonic Level Sensor is consist of two main parts viz. transmitter and receiver. The assembly is placed on the tank in which level is to be measured. The transmitter directs the sound waves to the matter and those waves gets reflected back from its surface. Receiver receives the waves and counts down the time delay between the transmission and back receive. From this data and some standard data like speed of ultrasonic sound in the air it finds the distance of level of matter from the sensor.

This sensor provides very fast and reliable data output. Whole answer is mainly dependent upon time delay or lag. The ultrasonic sound is created by the Piezoelectric crystal inside the sensor. It converts electrical energy to ultrasonic sound energy.

Types of Ultrasonic Level Sensor:

1. Continuous Level Sensor:

Continuous Level Sensor can monitor continuously for change in level. In this the phase of emission of waves, their reception and calculation of level is ongoing process.

2. Point Level Sensor

Apart from continuous level sensor, Point level sensor is fire up type. It emits the sound, receives it and calculates the depth for one time. Its name can explain it.

Advantages:

1. Non disturbing technique.
2. Can be used for wide range of things like solid and liquids with wide range of viscosity.
3. Low price.
4. High functionality.
5. Very accurate and low error.
6. Long life instrument.
7. Can measure the level of different liquids having different densities in same tank.

Limitations:

1. Sensor mounting must be properly done.
2. Tank should be free from obstacles otherwise it may cause error in measurement.
3. Result may get affected due to change in temperature or pressure inside the tank or container.

Applications:

1. Automatic pump control.
2. Flow measurement.
3. open channel flow measurement.
4. Used in water/waste applications.

Related Topics and Articles:

1. Ultrasonic Devices
2. Ultrasonic Distance Sensing
3. Ultrasonic Flowmeters

Principle of RVDT:

RVDT is used where precise angular movement is to be measured. RVDT uses the same principle as the LVDT except that, LVDT is for linear measurement while RVDT is for Angular one.

Construction and Working of RVDT:

RVDT is almost identical in the construction with LVDT. The ferrite core in LVDT is replaced by heart or cardiode shaped core. This core is mounted on the shaft or plunger which is capable of rotating. This rotational movement of the shaft creates the imbalance in the external circuit and this imbalance signal is used to measure the angular displacement of the shaft. RVDT give linear output up to displacement of +-40 degree. Then output starts becoming nonlinear.

Applications:

1. RVDT in the signal conditioning as RVDT Conditioner.
2. RVDT as the position sensor.

Examples:

1. Quarter Turn Valve.
2. Mail Sorters.
3. Fractional Shaft measurements.
4. Actuator position sensing in the Aircraft.
5. Marine, Constructional and Agricultural vehicles.

Advantages of RVDT:

1. Low cost.
2. Solid and Robust construction makes it to work in different environments.
3. No frictional resistance, so high accuracy over long time duration.
4. Negligible hysteresis.
5. Excellent reproducibility.

Disadvantages of RVDT:

1. Contact between plunger and measuring surface is always not possible.
2. RVDT provide linear output for about +-40 degree which limits its usability.

Related Topics and Articles:

1. Linear Variable Differential Transformer-LVDT
2. Ultrasonic Level Sensor
3. Ultrasonic Distance Sensing